U.S. Pat. No. 3,772,389, Lowrance, issued Nov. 13, 1973, discloses the reaction of phenols and carboxylic acids in the presence of a catalyst system consisting of a boron compound and sulfuric acid, to form the corresponding phenyl ester. Various boron compounds are disclosed, including boric anhydride. U.S. Pat. No. 4,271,311, Knickmeyer et al., issued June 2, 1981, discloses the reaction of phenols with carboxylic acids in the presence of a catalyst system consisting of a boron compound and certain alkali metal salts. Boric anhydride is among the boron compounds disclosed. The Lowrance and Knickmeyer patents are incorporated by reference herein.